Generally, an engine room of a vehicle is provided with an engine, a cooling means for cooling the engine, an air conditioning device, and the like. The cooling device, which is to cool the engine of the vehicle, is configured to include a radiator for cooling a coolant of the engine and a fan shroud generating an air flow of the radiator to improve heat radiation efficiency of a surface of the radiator, thereby further promoting cooling efficiency of the coolant.
The fan shroud is configured to blow air to an air cooling type heat exchanger such as the radiator, a condenser, or the like, of the vehicle in order to promote heat radiation of the air cooling type heat exchanger, and is classified into a pusher type and a puller type depending on a form in which the heat exchanger is disposed.
The pusher type is a type in which an axial-flow fan is disposed at a front side of the vehicle of the heat exchanger to forcibly blow air from the front of the vehicle toward the rear of the vehicle. Since air-blowing efficiency of the pusher type for the heat exchanger is low, the pusher type is used in the case in which a margin space behind the heat exchanger within the engine room is narrow. On the other hand, the puller type is a type in which an axial-flow fan is disposed at a rear side of the vehicle of the heat exchanger to pull air of a front side of the vehicle of the heat exchanger, thereby allowing the air to pass through the heat exchanger. Since air-blowing efficiency of the puller type is relatively higher than that of the pusher type, the puller type has been used in most of vehicles.
FIG. 1 is a perspective view of a fan shroud F according to the related art, and FIG. 2 is a front view of the fan shroud F according to the related art. FIG. 3 is a cross-sectional view of an air flow narrow space on a shroud 30 taken along line A-A′ of FIG. 2.
Referring to FIGS. 1 and 2, the fan shroud F fixed to a rear end of a heat exchanger in order to introduce air into the heat exchanger indicates an assembly of a fan 10 and a shroud 30, and is configured to include the fan 10 for air-blowing, a motor 20 for driving the fan 10, and the shroud 30 including a body 31 having a vent hole formed at the center thereof and a motor fixing part 32 fixing and supporting the motor 20 by a plurality of stators 33 extended from an inner peripheral surface of the vent hole in a radial direction.
In the fan shroud F having the configuration as described above, noise due to friction with air at the time of rotation of the fan 10 and rotation noise of the motor 20 are necessarily generated. Therefore, the development of a technology for reducing the noise due to the friction with the air by changing a shape of the fan 10 or a shape of the shroud 30 has been actively conducted.
Here, as illustrated in FIG. 2, the fan 10 of the fan shroud F has a circular shape, and the shroud 30 of the fan shroud F has a quadrangular shape in order to enclose the heat exchanger having a quadrangular shape, such that a distance between the vent hole and a circumferential part of the body 31 is short at upper and lower sides of the vent hole and is relatively long at left and right sides of the vent hole. That is, the body 31 may be divided into diagonal regions in which a length between the vent hole and the circumferential part of the body 31 is a first length L1 that is long, upper and lower regions 31b in which a length between the vent hole and the circumferential part of the body 31 is a second length L2 that is short, and left and right regions 31a in which a length between the vent hole and the circumferential part of the body 31 is a length between the first length L1 and the second length L2.
Here, as illustrated in FIG. 3, a portion from a distal end of the vent hole to the circumferential part of the body 31 is inclined in order to smooth a flow of air, thereby reducing overall noise depending on the flow of the air.
However, since the length between the vent hole and the circumferential part of the body 31 is relatively short in the upper and lower regions 31b, narrow spaces A1, which are narrow air flow spaces, are present, and the flow of the air is not smooth in the narrow spaces A1, which mainly causes blade pass frequency (BPF) noise.
The BPF noise is repetitive noise of a high range generated at the time of rotation of the fan, and even though the overall noise is reduced, in the case in which the BPF noise is generated, sensitive quality of a user is not satisfied. Therefore, recently, the development of a technology for reducing the BPF noise has been demanded.